ORIGINAL
Villalpando S et al
ARTICLE
Iron, zinc and iodide status in Mexican
children under 12 years and women 12-49 years
of age. A probabilistic national survey
Salvador Villalpando, MD, PhD, (1) Armando García-Guerra, MSc,(1) Claudia Ivonne Ramírez-Silva, BSc, (1)
Fabiola Mejía-Rodríguez, BSc,(1) Guadalupe Matute, Chem, (2) Teresa Shamah-Levy, MSc, (1) Juan A Rivera, MS, PhD.(1)
Villalpando S, García-Guerra A, Ramírez-Silva CI,
Mejía-Rodríguez F, Matute G, Shamah-Levy T, Rivera JA.
Iron, zinc and iodide status in Mexican children
under 12 years and women 12-49 years of age.
A probabilistic national survey.
Salud Publica Mex 2003;45 suppl 4:S520-S529.
The English version of this paper is available too at:
http://www.insp.mx/salud/index.html
Villalpando S, García-Guerra A, Ramírez-Silva CI, MejíaRodríguez F, Matute G, Shamah-Levy T, Rivera JA.
Estado de hierro, zinc y yodo en niños menores
de 12 años y en mujeres de 12-49 años de edad
en México. Una encuesta probabilística nacional.
Salud Publica Mex 2003;45 supl 4:S520-S529.
El texto completo en inglés de este artículo también
está disponible en: http://www.insp.mx/salud/index.html
Abstract
Objective. To describe the epidemiology of iron, zinc and
iodide deficiencies in a probabilistic sample of Mexican women and children and explore its association with some dietary and socio-demographic variables. Material and
Methods. We carried out in 1999 an epidemiological description of iron (percent transferrin saturation, PTS, <16%),
serum zinc (<65ug/dl) and iodide (<50 ug/l urine) deficiencies in a probabilistic sample of 1,363 Mexican children under 12 years and of 731 women of child-bearing age. Serum
iron, Total Iron Binding Capacity (TIBC) and zinc were measured by atomic absorption spectrometry, and urinary iodide
by a colorimetric method. Logistic regression models explored determinants for such micromineral deficiencies. Results. Iron deficiency was higher (67%) in infants <2 years of
age. Prevalence declined (34-39%) at school age. The prevalence for iron deficiency in women was 40%. Zinc deficiency
was higher in infants <2 years of age (34%) than in school-age
children (19-24%). Prevalence in women was 30%, with no
rural/urban difference. In women the likelihood of iron deficiency decreased as SEL improved (p=0.04) and increased
with the intake of cereals (p=0.01). The likelihood of low
serum zinc levels was greater in women and children of low
socioeconomic level (SEL) (p<0.02 and p=0.001) iodide deficiency was negligible in both children and women. Conclusions. The data shows high prevalence of iron deficiencyspecially in infants 12 to 24 months of age. It is suggested that
Resumen
Objetivo. Describir la epidemiología de las deficiencias de
hierro, zinc y yodo en una muestra probabilística de mujeres
y niños mexicanos y analizar algunas asociaciones con factores dietéticos y sociodemográficos. Material y métodos.
Descripción epidemiológica de las deficiencias de hierro (Porcentaje de saturación de transferrina <16%), zinc (<65ug/dl)
y yodo (<50ug/l orina) en una muestra probabilística de 1363
niños y 731 mujeres. Las concentraciones séricas de hierro,
y la capacidad total de saturación de hierro y zinc se midieron por espectrometría de absorción atómica, y el yodo por
un método colorimétrico. Los determinantes de tales deficiencias se estudiaron mediante modelos de regresión logística. Resultados. La deficiencia de hierro fue mayor (67%)
en niños <2 años de edad. La prevalencia disminuyó en los
escolares (34-39%). La prevalencia de deficiencia de hierro
en mujeres fue de 40%. La deficiencia de zinc fue mayor en
niños <2 años de edad (34%) que en escolares (19-24%). La
prevalencia en mujeres fue de 30%, sin diferencia rural/urbana. La probabilidad de tener deficiencia de hierro en mujeres disminuyó con el nivel socio-económico (p=0.04) y
aumentó con la ingestión de cereales (p=0.01). La probabilidad de tener concentraciones bajas de zinc sérico fueron
mayores en mujeres de nivel socioeconómico (SES) bajo
(p=0.02 y p=0.001). La prevalencia de deficiencia de yodo
fue casi inexistente tanto en niños como en mujeres. Conclusiones. Los datos demuestran una alta prevalencia de de-
(1)
(2)
Centro de Investigación en Nutrición y Salud, Instituto Nacional de Salud Pública, Cuernavaca Morelos, México.
Unidad de Investigación en Nutrición, Centro Médico Nacional, Instituto Mexicano del Seguro Social, México, DF, México.
Received on: August 20, 2002 • Accepted on: October 16, 2003
Solicitud de sobretiros: Dr. Salvador Villalpando. Avenida Universidad 655, Colonia Santa María Ahuacatitlán 62508 Cuernavaca Morelos, México.
E-mail: [email protected]
S520
salud pública de méxico / vol.45, suplemento 4 de 2003
Iron, zinc and iodide deficiencies in Mexican children and women
ORIGINAL
ARTICLE
in older children and women 12 to 49 years of age that iron
bioavailability is low. The prevalence of zinc deficiency was
also very high. The English version of this paper is available
too at: http://www.insp.mx/salud/index.html
ficiencia de hierro, especialmente en niños de 12 a 24 meses
de edad. Se sugiere que en niños mayores y en mujeres de 12
49 años existe una baja biodisponibilidad de hierro. La deficiencia de zinc fue tambien muy alta. El texto completo en
inglés de este artículo también está disponible en: http://
www.insp.mx/salud/index.html
Key words: iron deficiency; zinc deficiency; iodide deficiency;
preschoolers; school-age children; women of child-bearing
age; Mexico
Palabras clave: deficiencia de hierro; deficiencia de zinc;
deficiencia de yodo; niños preescolares; niños escolares;
mujeres en edad reproductiva; México
deficiency is the most common nutritional
I ron
deficiency worldwide. Although, anemia is the
drafting 6.6% of the 21 000 households originally selected.
The probability of selecting a given household (V)
to obtain blood samples from an individual of one age
group (w) was determined by the following formula:
best-known consequence of iron deficiency, it also produces impairments in mental development, in the ability to combat infections when occurring during early
childhood, and difficulty in performance of physical
work in later life.1 Mild zinc deficiency is associated
with growth retardation; it also alters the immune response, and increases de incidence of diarrhea and other infections.2,3
Ample information on the prevalence of stunting
in Mexico is available.4,6 However, assessment of the
nutritional status of micronutrients of Mexican populations is contained in a handful of studies, most
of which are not nationally or regionally representative.8-10 Information about the prevalence of micronutrient deficiencies is of utmost relevance for the design
and implementation of public nutrition programs.
This study describes the epidemiology of iron, zinc
and iodide deficiencies, based on determinations of
their concentrations in biological samples from a probabilistic sample of Mexican children under twelve and
women 12-49 years of age. Also, it explores the associations between these microminerals and dietary and
socio-demographic variables that may play a role as
determinants.
Material and Methods
Data were extracted from the database of the Mexican
National Nutrition Survey of 1999 (ENN-99). The methodology of this probabilistic survey was published in
detail elsewhere.6 Briefly, the sampling procedure included a randomized selection of households based on
the master household frame provided by Instituto Nacional de Estadistica, Geografía e Informática (INEGI).
Blood and urine samples were obtained in subsamples
of children under 12 and women 12-49 years of age, by
salud pública de méxico / vol.45, suplemento 4 de 2003
PS(VW)= PD(VW)•
S
Q
After prevalences were calculated, they were expanded to represent the original population.
The expansion factors were calculated based on
the characteristics of the Mexican population in 1995
according to census data published by Instituto Nacional de Estadística Geografía e Informática (INEGI).
Files of children under 12 and women 12 to 49
years of age containing information about their serum
iron, zinc and urine iodide concentrations, birth date,
gender, maternal education, dietary intake, socioeconomic level (SEL), ethnic origin, consumption of dietary supplements, and if they were beneficiaries of a
food assistance program (BFAP) were selected for the
present analysis. Maternal education was stratified into
five categories based on the education cycles completed: no schooling, primary school (6 years), secondary
school (9 years), high school or more (>12 years). Socioeconomic level was a continuous variable using a
construct based on a principal components analysis of
household possessions and characteristics. Ethnic origin was categorized as indigenous for families in which
at least one member spoke a native language.10 Dietary
supplements included vitamins and/or minerals (pills,
drops, etc.), or enriched food provided within a formal public nutrition intervention. Food assistance was
considered as present when the family or the study
subject were beneficiaries of any program providing
food in kind or at subsidized prices. Food assistance
programs included in the questionnaire were: Fidelist,
S521
ORIGINAL
distributing tortillas and Liconsa, distributing milk,
both at subsidized prices; and DIF (Desarrollo Integral
de la Familia [Integral development of the family]),
distributing free food baskets. PROGRESA (Programa
de educación salud y alimentación [Education, health
and nutrition program]) was not included because at
the time of the survey distribution of fortified food was
just starting.
Study design
Chronological age of children was divided into oneyear intervals. Women were categorized as pregnant
and non-pregnant. Subjects were categorized as rural
if they lived in a community of less than 2,500 inhabitants; all others were categorized as urban. The country
was divided arbitrarily into four geographic regions: the
North region included the states of Baja California,
South Baja California, Coahuila, Chihuahua, Durango, Nuevo León, Sonora and Tamaulipas. The Center
included the states of Aguascalientes, Colima, Guanajuato, Jalisco, México, Michoacán, Morelos, Nayarit,
Querétaro, San Luis Potosí, Sinaloa and Zacatecas. The
Mexico City region included the Federal District and
the nearby urban areas. The South region included the
states of Campeche, Chiapas, Guerrero, Hidalgo, Oaxaca, Puebla, Quintana Roo, Tabasco, Tlaxcala, Veracruz
and Yucatán.
Blood sample collection, preparation
and preservation
Blood samples were drawn from a vein in the forearm,
in evacuated glass tubes specially prepared for trace
elements (vacutainer, purple cap, evacuated tubes,
Beckton Dickinson Inc, Lakes, NJ, USA). Serum was
immediately separated on the household premises using a portable centrifuge EB8 (Hettich, Tuttlingen, Germany), and transferred into cryovials and preserved
in liquid nitrogen until delivered to a central laboratory. Although they were spot samples, more than 80%
were collected in the morning after at least two hours
of fasting. Subjects with evident signs of acute infections or other debilitating illnesses were not included
in the sample.
Methods for iron, zinc, iodide,
C-reactive protein determinations.
The concentrations of iron, total iron binding capacity
(TIBC), and zinc and C-reactive protein were determined in serum samples, and iodide was determined
in spot urine samples.
S522
Villalpando S et al
ARTICLE
Iron status. Serum iron and TIBC were estimated by
determining iron concentrations before and after incubating a serum aliquot with saturated iron solution and
then precipitating it with trichloroacetic acid. Determinations were made by atomic absorption spectrometry using an Analyst 300 spectrometer (Perkin-Elmer,
Norwalk, Ct, USA). Percent transferrin saturation (PTS)
was calculated dividing serum iron by TIBC, times
100.11,12 Because PTS is a more parsimonious indicator
of iron status than the other two measurements, it was
used in this research as the sole indicator of iron status. Iron status as indicated by PTS was graded into
the following categories: Normal: >20%; iron depletion:
16.1-20%; and iron deficiency: <16%.13
Serum Zinc. Serum zinc concentrations were determined by atomic absorption spectrometry using the same
instrument described for the determinations of iron.14 A
cut-off value of 70 ug/dl has been recommended15 to
assess zinc deficiency in children based on NHAENES II
results. Because blood samples in this survey were not
obtained necessarily after fasting, we used a cut-off value
of 65 ug/dl, as recommended by the International Zinc
Nutrition Consultative Group (IzincCG).
C-reactive protein. C-reactive protein was determined
by nephelometry using a commercial kit (Dade-Behring, Marburg, Germany). The cut-off point used to
detect abnormal values was >3 mg/dl, as suggested
by the manufacturer.
Urinary iodide. Iodide concentrations were measured
in the urine samples collected in hermetic cryovial and
frozen at –70°C, until determination by a colorimetric
method, based on the capacity of iodide to reduce ceric-amonium sulfate in the presence of arseniosus acid.
The urine sample was digested previously with ammonium persulfate.16
Cut-off concentrations of iodide to define deficiencies were those of ICCIDD/OMS/OPS/UNICEF17 i.e.,
normal: > 100 ug/l, low risk: 50-99 ug/l, moderate risk:
20-49 ug/l, and high risk: <20 ug/l.
Assessment of dietary intake
Dietary intake was assessed by a single 24-hour (24-h)
recall applied to the women. The dietary intake of children was assessed by 24-h recall applied to the mother.
Based on this single recall the consumption of food and
nutrients was calculated. Nutrient intake was calculated by multiplying the portion size in grams of a given
food by the nutrient content per gram of that food as
per food-composition tables. Food composition was
obtained from a data base which included micronutrient information from 7 published food composition tables18-23and from an unpublished composition table
salud pública de méxico / vol.45, suplemento 4 de 2003
Iron, zinc and iodide deficiencies in Mexican children and women
(Información Nutricional de Marinela, Marinela Company, Mexico City), all of which were pooled at the Instituto Nacional de Salud Pública, Mexico.
ORIGINAL
ARTICLE
insufficient to furnish reliable conclusions, thus they
are not presented in this analysis.
Children under 12 years of age
Data analysis
Description of variables was made by central tendency and dispersion statistics. The prevalence of each category of nutritional status of minerals included in this
analysis is presented as rates and confidence intervals.
The presence of a positive C-reactive protein determination (>3mg/dl) excluded iron and zinc values of that
individual from the analysis. Actual sample size for
any category presented here was expanded using a
population factor as described above.
Also, to identify potential predictors of the nutritional status for each mineral, we constructed logistic regression
models, which controlled for the clustered design of the
study. Individual minerals were coded as normal or
abnormal according to the following cut-off values: PTS<
20% and serum zinc <65 ug/dl, and introduced into the
models as dependent variables. Age, gender,
socioeconomic level, ethnic status, receiving food assistance
programs, and the daily intake of the following food
groups: cereals, meat, legumes, were introduced as
independent variables. Food intake was expressed as
portions of 100 grams consumed per day. Because of the
great co-linearity between socioeconomic level, maternal
education and height we choose include socioeconomic
level in the model, and not maternal education, height or
height/age. There are some difficulties in explaining the
association of nutritional status of micronutrients and dietary variables, because the latter are frequently associated with SEL. Controlling for SEL when examining
associations with diet may represent over controlling. Thus,
to avoid it we constructed two additional restricted models
in which only socioeconomic variables or dietary variables
were alternately introduced as independent variables.
Data entry was done using a Clipper-based program using data entry formats that included range and
contingency validation checks (version 5.01, Nantucket
TM Corporation, 1991, S.F., California). Descriptive analysis was run in SPSS for Windows (version 10.1.4; SPSS
Inc, Chicago, U.S.A., 2000). Regression models were
adjusted using Stata statistical software (V. 7.0 for Windows, Stata Corp, College Station, Tx, U.S.A. 2001).
Results
Data on 1 363 children and 731 women were obtained;
however, the sample size varies for each nutrient because of losses of samples or unrecoverable results (Table I). The sample size for pregnant women was
salud pública de méxico / vol.45, suplemento 4 de 2003
Iron status. The prevalence of overt iron deficiency (PTS
<16%) at the national level was highest in infants 12 to 24
months of age (66.6%). Although the prevalence of iron
deficiency declined progressively with age, it remained
very high in school-age children (33.8-38.7%). Prevalence of iron deficiency was higher in rural than urban children, differences were of at least 10 percent points, except
at 11 years of age. At that age a surge in the prevalence of
iron deficiency in urban children changed the direction
of the difference in prevalence relative to rural children
(p<0.05). Urban children were able to reduce their prevalence of iron deficiency in 33% at three years of age, while rural reduced it in only 16% (Table III). The North
(73.1%), center (87%), and South (75%) regions had the
highest prevalence in infants younger than two years.
Children from the North and center reduced their prevalence of iron deficiency by more than 30 percentage points by three years of age, while those from the South did
so by only 10 percent points at the same age.
In a logistic regression analysis the likelihood of
being iron deficient was not affected by SEL, Indigenous ethnicity, being beneficiary of food assistance
programmes, dietary intakes of cereals, meat or leguminous (Table V).
Zinc status
The prevalence of low serum zinc levels was highest
in children under of 24 months of age (33.9%) and it
declined progressively with age, maintaining a plateau during the school age (19.3-24.4%) (Table II). The
global prevalence of low serum zinc levels in rural
children under 12 years of age (40.0%) was twice that
of their urban counterparts (18.2%); however, the opposite occurred in children under of 24 months of age
(24.7 vs. 36.6%, respectively) (Table III). The highest
prevalence of low serum zinc levels after two years
of age occurred in the South region, at all ages (20.951.7%), while the lowest corresponded to the North
region (5.5-14.2%).
Logistic regression showed that the likelihood of
having low serum zinc levels was lower as SEL increased (OR=0.44, p=0.001), (Table V).
Iodide status
The prevalence of urine iodide concentrations compatible with severe iodide deficiency were not detected in
S523
ORIGINAL
Villalpando S et al
ARTICLE
TABLE I
SOME DESCRIPTIVE DATA ON THE SAMPLE OF CHILDREN UNDER OF 12 AND WOMEN 12-49 YEARS OF AGE.
NATIONAL NUTRITION SURVEY, M EXICO, 1999
Characteristics
Non-pregnant women 12- 49 years of age
BMI (kg/height2)
< 18.5
18.5 - 24.9
25 - 29.9
≥30
SEL**
Low
Medium
High
Residence
Urban
Rural
Age (years)
Total 731
Children under of 12 years of age
Gender
Male
Female
Age group
0.5 – 2
3–4
5–6
7–8
9 – 10
11
Residence
Rural
Urban
SEL**
Low
Medium
High
Total 1363
Sample
n
Expanded (Thousand)
n
%
16
314
221
161
112.8
3 175.5
2 438.5
1 443.1
1.6
44.3
34.0
20.1
252
234
245
2 289.1
2 211.1
2 826.7
31.2
30.2
38.6
452
279
731
7 326.8
5 397.3
1 929.5
7 326.8
73.7
26.3
28.9±9.4*
705
658
8 195.4
7 327.4
52.8
47.2
48
176
263
354
352
170
1 092.1
4 282.4
2 227.8
2 992.3
3 439.5
1 488.8
7.0
27.6
14.4
19.3
22.2
9.6
631
733
4 847.4
10 675.4
31.2
68.8
523
332
508
15 522.8
5 824.1
3 860.3
5 838.5
37.5
24.9
37.6
*Mean ± SD.
** Socioeconomic status was categorized into three levels, based on principal component analysis of household possessions and characteristics
children under 5 years of age, and the prevalence was
0.5% in school-age children. The remaining children
in the sample had iodide concentrations either within
the normal range or indicative of a low risk of deficiency. Data were not further disaggregated because
of the extremely low prevalence of abnormal values
(Table V).
S524
Women 12 to 49 years of age
Iron status
The prevalence of overt iron deficiency (PTS <16%) at
the national level was 40.5%, and was higher in the rural (51.8%) than in the urban women (36.4%, p<0.02)
salud pública de méxico / vol.45, suplemento 4 de 2003
Iron, zinc and iodide deficiencies in Mexican children and women
ORIGINAL
ARTICLE
TABLE II
PREVALENCE OF
(PTS) <16% AND OF ZINC DEFICIENCY
<65 UG/DL IN CHILDREN UNDER 12 AND NON-PREGNANT WOMEN 12-49 YEARS
OF AGE . N ATIONAL N UTRITION S URVEY , M EXICO, 1999
IRON DEFICIENCY AS BY PERCENT TRANSFERRIN SATURATION
AS BY SERUM ZINC CONCENTRATIONS
Age groups (years)
Iron
deficiency, as by
PTS <16%
Sample
n
Expanded (Thousand)
n
Percent saturation
of transferrin mean
Mean
95% CI
Children
0.5 - 2
3-4
5-6
7-8
9 - 10
11
Total
35
120
188
238
232
118
931
754
2933
1555
2016
2466
994
10718
66.6
48.1
37.2
33.8
35.5
38.7
41.4
*
(40.6, 55.5)
(31.5, 42.9)
(29.5, 38.2)
(28.1, 43.0)
(30.0, 47.4)
(38.2, 44.6)
14.0
17.7
19.0
20.6
19.8
20.2
18.9
(11.6, 16.53)
(16.4, 18.98)
(18.2, 19.90)
(19.2, 21.90)
(18.8, 20.81)
(18.5, 21.87)
(18.3, 19.49)
Non-pregnant
women 12-49 years
563
5618
40.5
(37.1, 43.8)
18.7
(17.9, 19.5)
Prevalence of low serum
zinc levels (< 65 ug/dl)
Children
Low serum zinc
Prevalence of
Iron deficiency (%)
%
95% CI
Serum zinc concentrations
(ug/dl)
0.5 - 2
3-4
5-6
7-8
9 - 10
11
Total
31
128
186
265
268
123
1001
796
3130
1558
2261
2706
1077
11528
33.9
32.9
21.4
19.3
21.6
24.4
25.3
*
(25.2, 40.5)
(15.6, 27.1)
(15.4, 23.1)
(16.5, 26.7)
(18.2, 30.7)
(22.8, 27.8)
69.5
73.7
76.2
76.9
78.6
78.0
75.9
(67.4, 71.6)
(69.4, 78.1)
(74.1, 78.2)
(75.6, 78.2)
(75.9, 81.3)
(75.5, 80.6)
(74.6, 77.3)
Non-pregnant
women 12-49 years
543
5329
29.7
(26.8, 32.6)
73.6
(72.6, 74.6)
* Insufficient sample size to complete calculations
(Table III). The most affected region was the South with
a prevalence of 50.9%; nevertheless, the prevalence in
the other three regions (31-36%) was also high. The prevalence of iron depletion (PTS >16<20%) was about 20%
in all regions, except Mexico City (13%) The summed
prevalence of any form of iron deficiency was more than
70% in the South and about 50% in the other regions.
In a logistic regression model the likelihood of
having iron deficiency was lower as SEL increased
(OR=0.77, p=0.04) and higher in those with higher cereals
intakes (OR=1.22, p=0.01). BMI, being beneficiary of
food assistance programs, ethnicity, or the intakes of
meat, legumes, fruits or vegetables did not affect the
risk of being iron deficient (Table V).
Zinc status
The prevalence of zinc deficiency (<65 ug/dl) was almost 30% in the national sample, with no significant
salud pública de méxico / vol.45, suplemento 4 de 2003
difference between urban and rural women (28.8 vs.
33.9%, respectively) (Table III). The highest prevalence of zinc deficiency corresponded to the South region (36.4%) and the lowest to the Mexico City region
(19.2%). The other two regions were intermediate.
The likelihood of having low serum zinc levels in
women was lower as SEL increased (OR=0.74, p=0.02).
No association was found with age, BMI, being beneficiary of food assistance programmes or with any of
the food groups introduced to the model. (Table V).
Iodide status
In only one case were the urine concentrations of iodide
compatible with severe deficiency. Normal values
(>100 ug/l) or values compatible with mild deficiency
(50-99 ug/l) were found in 98% of the samples. No
differences in the prevalence were found between
urban and rural women (Table IV).
S525
ORIGINAL
Villalpando S et al
ARTICLE
TABLE III
PREVALENCE OF
(PTS) <16%,
<65 UG/DL IN CHILDREN UNDER 12 YEARS
AND NON- PREGNANT WOMEN 12-49 YEARS OF AGE . NATIONAL N UTRITION S URVEY , MEXICO, 1999
IRON DEFICIENCY AS BY PERCENT TRANSFERRIN SATURATION
AND OF ZINC DEFICIENCY AS BY SERUM ZINC CONCENTRATIONS
Residence
Sample
n
Age (years)
Urban
Expanded
(Thousand) Prevalence
n
%
95% CI
Sample
n
Rural
Expanded
(Thousand)
Prevalence
n
%
95%CI
Iron deficiency prevalence
Children
0.5 -2
3-4
5-6
7-8
9 - 10
11
Total
19
68
97
129
124
61
498
486
2054
1016
1445
1628
686
7315
62.2
42.3
34.6
31.3
32.4
42.1
38.2
*
*
(28.5, 40.6)
(27.3, 35.4)
(23.2, 41.7)
*
(34.8, 41.5)
16
52
91
109
108
57
433
269
879
539
571
838
307
3403
74.6
61.5
42.3
40.2
41.7
31.2
48.3
*
*
(30.5 , 54.1)
(29.4, 51.0)
(29.4, 53.9)
*
(41.7, 54.8)
Non-pregnant wome
12-49 years
436
4134
36.4
(32.8, 39.9)
217
1484
51.8
(43.7, 59.8)
Low serum zinc prevalence
Children
0.5 - 2
3-4
5-6
7-8
9 - 10
11
Total
19
75
98
136
142
63
533
616
2097
986
1561
1783
735
7779
36.6
21.6
13.9
15.2
13.6
16.7
18.2
*
*
*
*
(9.4, 17.7)
**
(15.9, 20.5)
12
53
88
129
126
60
468
181
1033
571
700
923
341
3749
24.7
55.8
34.3
28.3
37.1
41.1
40.0
*
*
*
(18.3, 38.4)
(25.6, 487)
**
(34.0, 45.9)
Non-pregnant women
12-49 years
322
3804
28
(24.7, 31.4)
221
1520
33.9
(28.1, 31.8)
* Insufficient sample size to complete calculations
Discussion
Iron deficiency in children. The prevalence of iron deficiency was very high in all children but particularly
in those under 24 months of age. Iron deficiency was
25% higher than the prevalence of anemia (50%) reported for the same infants from the NNS-99. 24 Plausible explanations for such a high prevalence of iron
deficiency in this age group include: a) There is a high
prevalence of iron deficiency in women of reproductive age from the same households herein reported,
particularly those that were pregnant. The latter may
lead to development of limited fetal iron stores of their
offspring. b) Even milk from well-nourished mothers
does not meet the infant’s iron requirements after the
S526
first few months of life; iron status of the infant then
relies only on preexisting stores. c) Dietary transition
from lactation to the family diet frequently implies
weaning children with foods of low energy and iron
densities. 25 Thus, the higher risk for iron deficiency
occurs in the first years of life when children are less
able to eat a diet with a larger content of iron. In support of this notion we observed that although the prevalence of iron deficiency declined in both rural and
urban infants, rural infants reduced their prevalence
of iron deficiency two years after their urban counterparts. Such differences might be attributed to differences in the timing and quality of weaning diets
between the two groups. Iron deficiency in women of
childbearing age. The prevalence of iron deficiency in
salud pública de méxico / vol.45, suplemento 4 de 2003
Iron, zinc and iodide deficiencies in Mexican children and women
TABLE IV
PREVALENCE OF IODIDE DEFICIENCY AS INDICATED BY THE
12 YEARS
OF AGE. NATIONAL NUTRITION SURVEY, MEXICO, 1999
EXCRETION OF URINARY IODIDE IN CHILDREN UNDER
Urinary
iodide
ug/l
> 100
50 - 99
20-49
< 20
Total
Children (age in years)
0.5 - 4
5 - 12
n
%
n
%
14
4
0
0
18
83
17
0
0
100
529
37
18
1
585
91.5
5.9
2.0
0.5
100
Total
n
543
41
18
1
600
Non-pregnant women 12-49 years of age
> 100
50 - 99
20-49
< 20
Total
560
35
10
1
603
92.9
5.3
1.7
0.2
100
women was high in general but some distinctions are
in order. It was higher in rural residents and in those
living in the poorest (South) region of the country. Iron
deficiency was as high in school-age children as in
women suggesting that they share common dietary
insufficiencies. Higher daily intakes of cereals represented a risk for iron deficiency too, suggesting that
they may interfere with the availability of iron. Corn
and corn products were the most frequently eaten food
by this population, referred, both, as grams per day or
as kcal per day. 26 Corn is known to be one of the cereals with the highest content of phytic acid, a potent
inhibitor of the intestinal absorption of iron and other
divalent metals. Thus, it is very plausible that the negative association between the intake of cereals and iron
status of this population may be explained by the higher intake of corn phytates.
Nutritional interventions aiming to improve the
iron status of young children and women of childbearing age are urgent in order to reduce the deleterious
effects of iron deficiency anemia and other forms of
iron deficiency on growth, 27 mental development,28 immune ability to combat infections,29 and work capacity.30
Zinc nutritional status
The lower cut-off value, relative to those most frequently accepted,15 was chosen for this study based on the
recent recommendations of the IZINCG for non-fasting serum samples, as was the case for the serum samsalud pública de méxico / vol.45, suplemento 4 de 2003
ORIGINAL
ARTICLE
ples from this survey.16 In this study, we demonstrated
that the prevalence of low serum zinc affected more to
children living in the poorest regions and to those of
the lower SEL.The primary cause of zinc deficiency is
believed to be the inadequate intake of dietary zinc.16,31
It is difficult to meet dietary requirements for zinc in
populations where a large proportion of dietary intake
is derived from cereals such as corn (maize) and very
little food from animal sources.
Zinc deficiency has profound and far-reaching effects on the health and well being of humans. There is
a large body of convincing evidence linking zinc deficiency to childhood growth stunting,32 increased prevalence of common childhood infections such as
diarrhea and pneumonia,33 reduced appetite among
children,34 impaired neurobehavioral function,35,36 delayed sexual maturation among adolescents,37 poor
pregnancy outcomes including low birth weight, preterm deliveries, maternal delivery complications,38 and
impaired immune function of the neonate,39 and increased risk of infant mortality among low birth weight
infants.40 Despite these far reaching consequences,
much remains to be learned about efficacious methods to prevent zinc deficiency. Women of childbearing age may be at even higher risk of zinc deficiency
in comparison to other groups (e.g. adult men) due to
the higher requirements for zinc during fetal development and lactation.41
Iodide status
Given the results presented, the prevalence of iodide
deficiency is negligible in both, women and children.
Distribution of abnormal results was so scattered that
no remarks can be made relating to geographical distribution. We recognize that the scope of our study does
not allow us to distinguish micro regions where iodide
deficiency might be still high. Table salt iodination is
the most ancient public nutrition intervention in Mexico. Salt iodination has been mandatory by law for more
than 50 years; thus, it is not surprising to find such a
low prevalence of low urinary iodide levels. A note of
caution is in order, however, as we checked on the
iodide level of table salt and found (data not shown)
that industrially refined salt, but none of the other
forms available on the market complied with the
required levels of iodide.
In summary the prevalence of iron and zinc deficiency is very high in women of childbearing age and
children, especially those under two years of age. The
evidence indicates that poverty is the main underling
cause of iron and zinc deficiencies. The association
between some dietary factors suggests that the iron
deficiencies are related to low intake of the most bioS527
ORIGINAL
Villalpando S et al
ARTICLE
TABLE V
LOGISTIC
REGRESSION MODELS OF IRON AND ZINC STATUS ON POTENTIALLY PREDICTIVE
VARIABLES IN CHILDREN UNDER
Children
Variables
Iron (PTS)
N= 670
Age (months)
SEL*
BFAP‡
Indigenous ethnicity§
Cereals (100g/d)
Meat (100g/d)
Legumes (100g/d)
Zinc
N= 726
Age (months)
SEL 0.44
BFAP 1.12
Indigenous ethnicity
Cereals (100g/d)
Meat (100g/d)
Legumes (100g/d)
Women
Variables
Iron (PTS)
n= 553
Age (years)
Body Mass Index
SEL*
BFAP‡
Indigenous ethnicity§
Cereals (100g/d)
Meat (100g/d)
Leguminous (100g/d)
Zinc
n= 534
Age (years)
Body Mass Index
SEL 0.747
BFAP 1.714
Indigenous ethnicity
Cereals (100g/d)
Meat (100g/d)
Legumes (100g/d)
Odds ratio
12 YEARS OF AGE. NATIONAL NUTRITION SURVEY, MEXICO , 1999
p value
Odds ratio
Model 1
0.99
0.79
0.99
0.77
0.90
0.86
0.85
0.50
0.17
0.97
0.45
0.34
0.63
0.68
0.99
0.80
1.03
0.75
Model 3
0.30
0.17
0.91
0.41
Model 2
0.20
0.45
1.13
0.62
0.93
0.26
0.69
0.99
0.001
0.64
0.82
Odds ratio
p value
Odds ratio
Model 1
0.11
0.64
0.93
0.01
0.44
0.83
1.005
1.008
0.774
0.924
1.054
0.10
0.62
p value
1.03
1.753
1.277
0.68
0.16
0.63
Odds ratio
p value
Model 3
0.69
0.67
0.04
0.77
0.90
1.242
1.088
0.997
Model 1
Model 2
0.16
0.55
0.742
1.732
0.98
0.56
0.86
0.67
0.24
0.31
0.67
Model 3
Model 2
0.54
0.58
p value
0.88
0.73
0.86
0.99
0.001
0.66
0.82
1.00
1.10
0.85
1.018
0.988
0.03
0.07
0.991
1.043
1.016
0.909
Odds ratio
Model 2
Model 1
1.008
1.011
0.815
0.880
0.961
1.228
1.126
0.965
p value
1.018
0.988
0.02
0.06
1.015
0.01
0.56
0.98
Model 3
0.16
0.54
0.97
1.097
0.963
0.958
0.19
0.68
0.85
* Socioeconomic status is a continuous variable, based on principal component analysis of household possessions and characteristics (mean= 0, SD= 1)
‡
BFAP (beneficiary of food assistance programs). Belongs to a family receiving corn tortillas or milk at subsidized prices, or free food baskets (Beneficiary=
1 and not beneficiary=0)
§
Indigenous ethnicity was defined when a woman 12-49y in the household spoke a native language (1=yes and 0=no)
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salud pública de méxico / vol.45, suplemento 4 de 2003
Iron, zinc and iodide deficiencies in Mexican children and women
available forms of the mineral, and to the intake of dietary iron and zinc inhibitors. Aggressive interventions
are imperative to correct iron and zinc deficiencies and
by so doing avoid their deleterious effects .
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